Activity stream, email notifications, and mobile app notifications are all customized on a user level - not a system level.
Select Activity Stream from the left side menu, then select the GEAR icon as seen below.
Choose from the Notification Settings options, then check or uncheck the items from each list as needed. Emails in particular are frequently sent; this will reduce the number of daily emails sent from the donotreply@blackboard.com address.
The following two Blackboard help pages break down what the settings control if you are a student or an instructor (please note we do not and will not ever use SMS).
Regarding the daily email notification, we cannot turn it off - if a user does not want an email notification, they must uncheck EVERY checkbox under the email tab (see the above screenshot).
Explanation for Students:
https://help.blackboard.com/Learn/Student/Ultra/Stay_in_the_Loop/Notifications#ultra_choose
Explanation for Instructors: